This invention is generally related to U.S. Pat. No. 3,721,894 entitled Regulator Control issued to Robert W. Beckwith and to U.S. Pat. No. 4,323,838 issued to Robert D. Pettigrew; the disclosure thereof being incorporated herein, by reference.
Load tap changing (LTC) transformers which automatically adjust to maintain a constant voltage are utilized in electrical power transmission systems for monitoring and controlling the voltage output. In such systems, any changes from a predefined voltage bandwidth are monitored and means are provided for changing the tap of the associated power transformers to regulate or bring the voltage within the selected bandwidth.
Tap changing transformer controls commonly provide means to change tap selector switches to contact a point of desired potential. For example, should the voltage in the electrical power transmission system go below a selected potential, provision is made to energize an associated motor to drive tap selector switches to make contact to a point of higher potential. Should the voltage go above the selected potential the motor is energized to drive the tap selector switches to make contact with a point of lower potential.
In recent years, the electric utility industry has become increasingly conscious of the need for reactive power management. Numerous systems and methods for obtaining improved active power monitoring and control have been developed. Various algorithms are known including linear and non linear programming which can optimize voltage control of electrical power systems. Normally the highest priority control objective is to eliminate violations of preset voltage limits, a second objective is to minimize those voltage violations that cannot be eliminated; and a third objective is to minimize the active transmission losses of the system.
In the prior art systems, devices with local intelligence such as load tap changing transformers, and automatic switching capacitors adjust voltages based on values sensed at their specific locations. As transmission systems become more complex and more fully utilized, these localized solutions are often not adequate, since a change at one point on the system can, and does, significantly affect other parts of the system. Accordingly, an integrated, generalized automated process and controls are necessary to continuously maintain the voltage limits required throughout the system. A flow diagram generally outlining the foregoing type of process is depicted in FIG. 3. Referring to FIG. 3 when voltage discrepancies are sensed, corrective activity is initiated. Processing of the algorithms indicates whether a feasible solution is available. If there is a feasible solution this data is coupled as an input to the control implementation device. If there is no feasible solution the data is fed as an input to the control implementation device as an input to minimize the violations. When there are no voltage discrepancies, a process is initiated to provide an input to the control implementation device for purposes of minimizing transmission losses to meet the third objective stated above.
The philosophy of the system mentioned above is discussed in the article "Optimal Real-Time Voltage Control", IEEE Transactions on Power Systems, Vol. 5, No. 3, August, 1990 pages 750-758 by S. A. K. Chang et al. The present invention relates particularly to unique apparatus and circuitry for providing a control implementation device as indicated in FIG. 3.